Argon laser-induced ocular hypertension: animal model of ocular inflammation

There is substantial evidence that prostaglandins (PG's) mediate acute elevations of intraocular pressure (IOP) due to laser irradiation of the iris. In the present study, we determined the optimal laser parameters needed to produce the maximal rise in IOP in anesthetized rabbits. Application of argon laser (0.75 watts, 0.5 sec. duration, and 8 spots of 500 micron size) to the iris of pigmented rabbits elicited an acute rise in IOP and miosis accompanied by an increase in aqueous protein concentration. This response was followed by a delayed ocular hypotension that lasted for more than 3 days and returned to baseline by day 5. The onset of ocular hypertension occurred within 15 min. and remained elevated for at least 90 min. The laser induced rise in IOP was related more to the number of laser spots applied to the iris than to the intensity of the total laser energy utilized. Pretreatment with either indomethacin or flurbiprofen produced a dose dependent inhibition of ocular hypertensive response and significantly reduced aqueous protein concentration. Indomethacin (0.01-30 mg/kg) was administered intraperitonially 1 hr. before laser treatment and flurbiprofen (0.03-0.3%) was administered topically 45 and 15 min. prior to laser application. The hypertensive response was reduced by more than 90% of control after both drugs, whereas the delayed hypotension was significantly antagonized only at the highest dose of indomethacin. Neither indomethacin nor flurbiprofen altered the maximum miotic response to laser irradiation of the iris. However, 0.3% flurbiprofen and 30 mg/kg indomethacin significantly increased the recovery rate of the miotic pupil. The results of this study support the contention that argon laser induced ocular hypertension may provide a quantitative assessment of inhibition of prostaglandin mediated responses.